textproduct: Albany

WHAT HAS CHANGED

The severe weather threat has ended for the entire region this evening, as a cold front has pushed south resulting in stabilizing conditions this evening.

07

KEY MESSAGES

1) A few strong to severe thunderstorms possible south and west of the Capital Region this afternoon into this evening with an isolated flash flood threat there as well.

2) Additional rounds of showers and thunderstorms late Wednesday afternoon/evening into Thursday with some strong/severe thunderstorms (Wed-Wed night) and isolated to scattered instances of heavy rainfall/flash flooding possible.

3) Generally tranquil weather with near to slightly below normal temperatures expected Friday into early next week.

DISCUSSION

KEY MESSAGE 1...As of 2:40 PM EDT...Broad upper ridge is located over the center of the country, with several impulses tracking along its northern periphery over the next few days. One of those moved through this morning, with another weak impulse back over the eastern Great Lakes tracking to the southeast over the next few hours. At the surface, a stationary/warm front is located near our southwestern border with BGM across Ulster and Dutchess Counties. Near the front, there has been some breaks of clearing that have allowed 1500-2000 J/kg of SBCAPE to develop with steepening mid-level lapse rates. This unstable airmass is overlapping with 40-45 kt of effective deep-layer shear per the latest SPC Mesonanalysis. The approaching shortwave impulse, low-level front, differential heating along the front, and outflow from showers located near/just southwest of I-90 could act as lifting mechanisms leading to CI over the next couple of hours.

If/when convection develops, discrete supercells will be possible, with the main threats being damaging winds and large hail. An isolated tornado can't be ruled out, with the greatest concern where flow is more backed in N/S oriented river valleys. SPC has maintained a slight risk for southwestern Ulster and Dutchess Counties. Greatest threat will exist through early evening, at which points convection should move off to the south of our area. Locally heavy rainfall will also be possible with any of these cells. WPC has maintained the marginal risk ERO today for much of our area, although the threat is really limited to just the southwestern corner of our CWA, roughly the same as where the SPC slight risk is. Highs this afternoon will range from around 80 near I-84 to the 60s across northern areas.

Convection should end this evening as sfc high pressure builds in from the northeast. Some patchy fog/mist/drizzle will be possible overnight with some low-level moisture trapped beneath a developing inversion, with lows in the 50s to low 60s.

KEY MESSAGE 2...Tomorrow is now looking relatively dry for our region through at least mid to late afternoon. The sfc frontal boundary will retreat well south and west of our region tonight with no real large-scale forcing through tomorrow as heights aloft actually rise through the morning. The sfc high to the E/NE will result in low-level cool easterly flow into the region and abundant cloud cover, which should help keep temperatures in the 60s (terrain) to 70s (valleys). We went a couple degrees below the NBM for daytime highs tomorrow. There are some signals that a weakening MCS may track south of the region in association with a weak upper impulse during the day, but not expecting any impact locally from this feature.

Tomorrow evening and night into Thursday, a stronger uper impulse will be tracking over the top of the upper ridge, along with an associated MCS that is expected to develop over southern Canada. Elevated instability looks to increases to 500-1000 J/kg ahead of this MCS tomorrow evening into tomorrow night as there are some hints of a remnant EML layer tracking overhead. Given this and impressive unidirectional deep-layer shear, we are expecting convection to be able to sustain itself as it tracks across our region tomorrow night. There doesn't look to be much surface- based instability, so wind threat actually looks lower than we might typically expect. However, large hail will be possible with any stronger storms given the elevated instability, relatively cool low- levels, and strong deep-layer shear/straight hodographs. SPC has maintained the marginal risk for severe for western areas tomorrow, but an expansion further east is possible over the next 12-24 hrs or so.

There is also a threat for locally heavy rain leading to flash flooding tomorrow evening into Thursday. PWATs remain elevated at around 1.8-2.0 inches. The core of the MCS should track through the region relatively quickly with fast flow aloft, but along the edges of the MCS there is more potential for backbuilding and training, and Corfidi upshear vectors are fairly slow at 10-15 kt so this will have to be watched. WPC has kept the slight risk ERO for the western Mohawk Valley and far southern ADKs , with a marginal risk for the rest of the region. Rainfall rates of over 1" per hour with total rainfall amounts generally around 0.5 to 1.5", with some locally higher amounts of 2-3" not out of the question where any training occurs. So, isolated to possibly scattered instances of flash flooding can't be ruled out, although potential for main stem river flooding looks very low (<10%). With just isolated to possibly scattered flash flood threat and some uncertainty in exact track of the MCS, did not feel a flood watch is warranted at this time.

Thursday forecast remains somewhat nebulous, and will likely depend on exactly how the overnight convection evolves. Most numerical guidance suggests that our southern areas could destabilize Thursday afternoon, especially if the convection is a little slower to track E/SE of our region. Deep-layer shear still looks impressive with 35- 45 kt. So, parameter space on paper appears favorable for severe weather, but mid-level drying and subsidence may help to counteract CI and limit the severe threat. This would be especially true if the overnight convection pushes further south of our region Thursday morning. SPC was leaning towards this solution with their overnight D3 convective outlook, opting to keep us in general thunder. However, given the conditional severe threat, expansion of the marginal risk further north into our area remains possible.

KEY MESSAGE 3...Thursday night into Friday, the front finally pushes well south of our region, thus ending the threat for severe weather through the remainder of the forecast period. An upper trough/ULL nearby could lead to a few isolated showers Friday into the weekend, especially for eastern areas where there are some hints for an inverted trough to develop as sfc low pressure tracks into the Gulf of Maine. High pressure then builds down from the north behind the departing ULL for the second half of the weekend into early next week, resulting in dry conditions area-wide. Temperatures looks to remain near to slightly below normal with low-level northerly flow.

AVIATION /00Z WEDNESDAY THROUGH SUNDAY/

Through 18z Wednesday...MVFR cigs in place to start the period early this evening. Other than some patchy drizzle, there will be a few -SHRA moving across KPOU through around 02z. Otherwise, it will be mainly dry through the rest of the 24 hour TAF period. Cigs will gradually lower to IFR levels by later this evening and last through the night into Wednesday morning. Vsbys will generally be VFR, with periods of MVFR associated with some mist tonight. Cigs are expected to improve to MVFR levels by Wednesday afternoon. Winds will be variable around 5 kt or less tonight, becoming southeast around 5-10 kt on Wednesday.

Outlook...

Wednesday Night: High Operational Impact. Definite SHRA...TSRA. Thursday: High Operational Impact. Definite SHRA...TSRA. Thursday Night: No Operational Impact. NO SIG WX. Friday: No Operational Impact. NO SIG WX. Friday Night: No Operational Impact. NO SIG WX. Saturday: Low Operational Impact. Slight Chance of SHRA. Saturday Night: No Operational Impact. NO SIG WX. Sunday: No Operational Impact. NO SIG WX.

ALY WATCHES/WARNINGS/ADVISORIES

CT...None. NY...None. MA...None. VT...None.